Molten metal dispensing apparatus



May 24, 1966 F. 1.. BURKETT MOLTEN METAL DISPENSING APPARATUS Filed May29, 1963 INVENTOR. Fran c115 L. Burke/z QTTORNEYS 3,252,187 MOLTEN METALDISPENSING APPARATUS Francis L. Burkett, Breckenridge, Mich., assignorto The Dow Chemical Company, Midland, Mich., a'corporation of DelawareFiled May 29, 1963, Ser. No. 284,229 6 Claims. (CI. 22-70) Thisinvention relates to the handling of molten metal v and particularlyrelates to an apparatus for the delivery of successive predeterminedamounts of a molten metal to a utilization device.

Several apparatuses have been disclosed concerning the delivery ofmeasured amounts of molten metal to a utilization device. In general,these devices comprise one or more separate components, such as, forexample, a valve component and pump component, connected to each otherby conduits, the so-connected components in turn being attached to adelivery pipe. In addition, these apparatuses are relatively complex,having usually a number of moving and close tolerance parts andirregular shapes.

Because of these factors, malfunctions and breakdowns are frequent, andfabrication and assembly diificult, thus requiring a high level ofmaintainance, detailed construction, and experienced operatingpersonnel. In addition, a complex apparatus consisting of severalindividual components connected to one another by conduits and the likeis understandably more difficult to install and to remove from thesupply of molten metal in which it is partially or wholly submergedshould the apparatus need repair or replacement.

An object of the present invention is to provide an improved, simple andeconomical apparatus for the delivery of a succession of predeterminedsubstantially equal amounts of molten metal, to for example, the shotwell ,amounts of molten metal to, for example, the shot well of a diecasting machine.

A related object is to provide such an apparatus having a minimum ofmoving and close tolerance parts and a compact integrated pump-valveunit component which will require little maintenance and which will bereadily removable as a unit from the supply of molten metal in which itis submerged.

Another object of the invention is to provide an improved apparatus forthe delivery of molten metal which during operation will not causeturbulance in the pot containing the supply of molten metal in which theapparatus is partially submerged.

These and other objects and advantages will become apparent from thefollowing detailed description when read in conjunction with theaccompanying drawings depicting one embodiment of the invention wherein:

FIGURE 1 is a side elevational view partially cut away and partly insection of an apparatus in accordance with the present invention. 1FIGURE 2 is plan view of the integrated pump-valv delivery unit of theapparatus of the present invention taken along line 22 of FIGURE 1.

FIGURE 3 is a detailed fragmentary view in side elevation showing amodification of the connection of the lip of the pot with the apparatusof the invention from that shown in FIGURE 1.

I Normally, the apparatus of the present invention is used inconjunction with a melting or supply pot containing a supply of themolten metal intended to be dispensed, the apparatus, primarily theintegrated pumpvalve unit thereof, being at least partially submergedtherein. In addition, the pot is normally equipped with a suitable means(not shown) to maintain the metal in said'pot in a molten liquid stateby the application of heat and may either be opened or closed at the topas United States Patent desired or required. An appropriate protectiveflux cover or inert atmosphere on or immediately above said molten metalin the pot may also be used depending on the nature of the molten metalin the pot.

In general, the molten metal dispensing apparatus of this inventioncomprises an integrated submersible pumpvalve unit having an inlet andoutlet means, a valve assembly part and a centrifugal pump portion(including a drive shaft which extends out of said pump through theinlet means), support means for suspending the unit in a supply ofmolten metal, means to provide power for operating the pump portion ofsaid unit, actuating means for opening and closing the valve assemblypart of the integrated pump-valve unit, and, a delivery pipe to whichthe unit is attached at or near the outlet meansprovided in thepump-valve unit.

With respect to the aforesaid integrated unit, the pump portion thereofcomprises, in general, a rotatable impeller as the core element. Theimpeller is attached to a drive shaft and is surrounded by a pump casingwhich has an inlet and outlet for receiving and dispersing molten metal.The pump portion, in addition, serves to hold and position the belowdescribed valve seat of the valve assembly portion. The drive shaftextends from the impeller, out of the pump casing, and through saidinlet, thus through the valve seat, where it is attached at its otherend to the powering means. The valve assembly part comprises, -ingeneral, a circular valve seat disposed around and spaced from theaforesaid drive shaft, and a movable rotatable valve head which isattached to the drive shaft immediately above the valve seat and isadapted to engage with the valve seat when the unit is not in operation.Thus, when the pump and drive shaft are not rotating, a substantiallytight seal will be made by the engagement of said valve seat and head,thereby preventing molten metal from entering the pump portion. Adetailed de scription concerning the operation of the apparatus inaccordance with the present invention follows hereinafter.

Referring now to the figures, one embodiment of the present invention isshown therein, the integrated pumpvalve unit 10 of the apparatus beingsuspended in a supply pot 11 containing molten metal 12 by a pluralityof vertical supports 13 which are attached, as by welding, for example,to one or more horizontal cross members 14. These cross members are inturn attached, for example, by bolts 15 to the lip 16 of the supply pot.Alternatively, it has been found very convenient, particularly when itis desired to remove the entire apparatus from the pot, to attach thecross members 14 to the pot lip'16 by freely movable locators 17 such asshown in FIGURE 3.

The aforesaid pump portion of the integrated unit 10 of the presentapparatus comprises a rotatable impeller 18 which is coupled to thelower end of a vertical movable drive shaft 19 which extends upwardthrough-the pump casing, indicated generally by the numeral 48, abovethe level of the molten metal 12 where, at its upper end, it ispreferably quick detachably coupled by means of the coupling 20 to apowering means such as, for example, either an air or electric motor 21.The motor 21 is rigidly coupled to a yoke plate 22 which in turn isattached at each end thereof to a vertically movable piston device 23and 23a. The devices 23 and 23a, when actuated, raise or lower the motor21 and drive shaft 19 to open or close the valve head 36 on the valveseat 34, as will be. discussed more fully below. Although thelongitudinal axis of the drive shaft 19 and impeller 18 is shown ascorresponding to that of the pump casing, such correspondence is notcritical and, therefore, the axis of the impeller 18 and drive shaft 19need not be coaxial with that of the pump-valve unit.

Surrounding the impeller 18 is a two-piece, essentially circular, rotarypump casing comprising an inverted cup shaped top section 24 and a cupshaped bottom section 25, the top section having an inlet bore 26 and anoutlet bore 27. The outlet extends more or less tangentially withrespect to the peripheral path of the rotating impeller 18 through aprojection 28 of the cylindrical vertical wall of the assembled casingand is located as nearly adjacent to the upper impeller position, as isdescribed below, as possible. The casing sections 24 and 25 are heldtogether by threaded bolts 29 from theupper side 30 of the unit and arereceived by tapped threaded bores 31 in the bottom section 25 of thecasing to allow the two said casing sections to be drawn together andsealed tightly at their mating edges 32 to form an assembled pumpcasing. Of course, other conventional fastening means may also beemployed to hold the two said portions together, such as welding, forexample.

Constructed in the top section of the pump casing is a circular recesswhose edge 33 provides a continuous shoulder to support thereon thevalve seat 34 of the valve assembly, as will be more fully describedbelow. The internal cavity of the assembled pump casing which theimpeller occupies must be of such depth (longitudinal dimension) as topermit vertical movement of the impeller such that an upper position (asshown by the solid lines in FIGURE 1) and a lower position (shown bydotted lines in FIGURE 1) of both the valve and impeller 18 ispermitted. The reason for this will be explained below and will becomemore obvious as the description of the apparatus proceeds. Preferably,the depth of the cavity should be approximately equal to twice theheight of the impeller blades.

' The valve assembly part of the apparatus'is integrated with the pumpportion of the unit to constitute the integrated pump-valve unitcomponent of the present apparatus. The valve assembly comprises acircular valve seat 34 having a beveled edge 35, the seat 34 beingsymmetrically disposed around and spaced from the drive shaft 19 andheld by a friction fit in the aforesaid recessed edge 33 provided'in thetop section of the pump casing 48, and a movable valve head 36 which isadapted to mate with and engage the valve seat 34 'to form therewith atight seal without a sticking or Wedging elfect upon being engaged. Thevalve head 36 is rigidly attached to the drive shaft 19 immediatelyabove the valve seat 34, for example, by welding. When the impeller 18and drive shaft 19 are in the lowered position, as indicated by thedotted lines in FIGURE 1 (and not rotating), the valve head 36 engagesthe valve seat to form a substantially tight fit, thereby preventing anymolten metal from entering the molten metal inlet 26 provided by thecircular opening leading into the casing formed by the valve seat. Thevalve head 36 is fixed on the drive shaft at a distance sufficientlyabove the valve seat such that when the impeller and shaft are rotatingand thus are in the upper position (raised by devices 23 and 23a) asshown in FIGURE 1, a sufficient clearance is provided to allow anadequate supply of molten metal 12 to flow. between the valve head 36and seat through the molten metal inlet 26. As molten metal enters thepump casing, the rotating impeller 18 forces the molten metal ultimatelyinto the receptacle of a utilization device, such as, for example, intothe shot well 50 of a die casting machine 51 through a delivery pipe 37.

The delivery pipe 37 is normally equipped with a heating means, such,for example, electric coils 38, to maintain the molten metal in the pipeat a temperature at least slightly above its liquidus. The lower end ofthe pipe 39 is attached, for example, by welding, to the pump casing atthe outlet bore 27 which is housed by the aforementioned projection 28.It has been found convenient to equip the delivery pipe with a slipjoint 41 located near the place where the pipe is coupled to the pumpcasing. The slip joint has rings 42 with conical edges which mate. Byso-doing, should it become necessary to withdraw the integrated unit 19entirely from the molten metal supply either for replacement or repairs,the pipe is easily disconnected from said unit leaving only a shortportion of said pipe attached to the unit it Preferably the slip jointrings 42 should be constructed of material possessing higher strength atelevated temperatures than that of the thin adjoining delivery pipewalls. Such a material may be, for example, a high temperature toolsteel which comprises about 18 percent by weight tungsten, about 4percent by weight chromium, and about 1 percent by weight vanadium, thebalance being essentially iron.

The discharge end 43 of the delivery pipe 37 is preferalbly equippedwith a hinged upwardly swinging shroud 44 within which, immediatelyabove the level 45 of molten metal in the pipe, is maintained anatmosphere of a non-oxidizing gas, such as, for example, argon, in orderto prevent burning of the material and formation of an oxide skin on thepip-e walls. The upwardly swinging shroud 44, shown in the upwardposition in FIGURE 1 by the dotted lines conveniently permits rods to beinserted from the discharge end 43 of the pipe to unclog it-should thatbecome necessary.

The actuating means for opening and closing the valve assembly portionof the integrated unit, the discussion thereof which has purposely beenomitted to this point because it closely relates to operation of theapparatus which is discussed below, comprises, a means such as, forexample, dual air operated piston devices 23 and 23a rigidly attachedtogether by a yoke plate 22 on which the powering means rests and isattached such that the piston devices 23 and 23a raise or lower themotor 21, therefore, also the drive shaft 19 with the valve head 36attached. The valve assembly either opens or closes depending on thedirection and amount of vertical movement of the piston devices 23 and23a. In practice, as will be discussed below, both the air pistons andthe motor are coordinated such that when the motor is operating, i.e.,the drive shaft and impeller are being rotated, the pistons are in theraised position,

as shown in FIGURE 1, thus raising the valve head fromthe valve seat,whereas, when the motor is not operating, the pistons are in the lowerposition, as shown by the dotted lines in FIGURE 1, thus closing thevalve.

Preferably, the actuating means and powering means are closelycoordinated by conventional timing means 46 with, for example, theoperation of the die casting machine 51, such that a programmed timesequence is established whereby a rapid succession of predeterminedamounts of molten metal can be dispersed to the shot well 50 of said diecasting machine 51 or to some other utilization device.

For ease in disassembling the casting apparatus of the presentinvention, both the impeller and powering means are preferably quickdetachably coupled to the lower and upper end of the drive shaft,respectively.

In operating the embodiment of the apparatus of the present invention asdepicted in FIGURE 1, the integral pump-valve unit 10 with the deliverypipe 37 attached is submerged, after preheating, into the pot 11containing the molten metal 12 to be handled so that said unit is belowthe level of the molten metal and r the inlet opening 26 is locatedsubstantially at the center of the molten metal supply. When initiallysubmerged, the valve assembly portion of the unit should be open, thatis, the impeller should be in the raised position, but the pump impellershould not be rotating whereupon, the pump impeller is immediatelyrotated, not only to create enough pressure in the pump to maintain thehead of molten metal in the pipe, but also to force additional moltenmetal into the pipe whereby a like amount overflows by displacement intothe shot well of the die casting machine. When the desired amount ofmolten metal-has been dispensed to the shot well, the

dual air pistons are again actuated this time'to lower the poweringmeans, thus lowering the drive shaft with the valve head attached,thereby closing the valve assembly, whereupon, the rotary action of thepump is ceased. Thereafter, the piston 52 of the shot well 50is'actuated to force the dispersed amount of molten metal therein int-othe die casting machine mold. After solidification of the dispersedamount of molten metal, the mold is opened and the cast piece ejected,followed by closing the mold, and actuating the air pistons upward againwhile practically simultaneously operating the impeller to dispensestill another shot of molten metal into the shot well followed byclosing the valve assembly and again operating the piston of the-shotwell to force the dispersed molten metal into the mold, thereby to makestill another casting. The total operation is repeated in a rapidtime-sequenced manner to produce the desired number of cast pieces.

In practice, the rotating action of the impeller should be commenced aninstant previous to disengaging the valve head 36 from the seat 34inorder to maintain the desired level 45 of molten metal in the deliverypipe. Conversely, impeller rotation should be continued an instant afterthe engagement of said valve head and seat for the same reason.

Inasmuch as both the valve seat 34 and valve head 36 are probablysubjected to an increased rate of wear due to the fact that in operationthe valve head will rotate slightly while in contact with the seat 34,both when opening the valve assembly and closing it, at least the matingsurfaces of these two parts should preferably be Stellite coated, forexample, to prolong the operable life of the valve assembly. Such aStellite coating also serves to reduce deformation of these parts uponimpact with each other.

Due to' the compactness of the apparatus of the present I invention andsince it has comparatively few moving and close tolerance parts, repairthereof, or a complete replacement, is easily eifected Without a timeconsuming and involved procedure.

For ease in accomplishing temperature determinations, for example, inthe integral pump-valve unit 10 of the present invention, one of thevertical support members 13 may be built with a hollow core so that thewire of a thermocouple 47 may be inserted therein and connected to saidintegral unit to record temperatures. However, other sensory devices andleads may also be employed.

The materials of construction to be employed in the parts of theapparatus which are to contact molten metal such as, for example, thepump casing of theintegral unit, vertical supports, and delivery pipe,are those which will be durable in the presence of the molten metalintended to be handled and which are resistant to erosion and corrosion.When employing molten magnesium, for instance, mild steel or,preferably, the high temperature chrome steels such as, for example, 430stainless are satisfactory for all surfaces which are to contact saidmolten magnesium. The drive shaft on, the other hand should beconstructed of the aforementioned tool steel for proper strength.

It should be understood that various changes and modifications can bemade in the apparatus of the present invention without departing fromthe substance and scope thereof, and it is further understood that thepresent invention is not limited to the embodiment thereof as shown inthe appended drawings.

I claim;

1. An apparatus for the delivery of molten metal to a utilization devicewhich comprises a submersible integrated pump-valve unit having a pumpassembly portion, said pump assembly portion including a drive shafthaving an upper end and a lower end, an impeller, said impeller havingthe same longitudinal axis as said drive shaft and being coupled to saiddrive shaft, a pump casing having a top section, bottom section, .andside walls, said casing surrounding said impeller and having suificientdepth to permit substantial vertical movement of the impeller inconjunction with the drive shaft, said casing having an inlet bore meansin said top section, said drive shaft extending through said inlet bore,and an outlet bore extending through said side wall, a valve assemblypart, said valve assembly part including a valve seat disposed in saidinlet bore and a valve head, said valve head surrounding and beingrigidly coupled to said drive shaft; supporting means to suspend theapparatus in the molten metal to be dispensed; powering means to providerotary power for the pump portion; actuating means for raising andlowering said drive shaft whereby said valve assembly portion is openedand closed; and a delivery pipe attached to the pump casing at saidoutlet bore;

2. The apparatus of claim 1 wherein, the longitudinal axis of the pumpcasing and inlet bore corresponds to that of the impeller and driveshaft.

3. The apparatus of claim 1 wherein, the mating surfaces of both thevalve head and seat are provided with a Stellite coating.

4. The apparatus of claim 1 wherein, the valve seat is symmetricallydisposed around and spaced from the drive shaft and held by a frictionfit on a recessed edge in the inlet bore.

5. The apparatus of claim 1 wherein, the powering means and actuatingmeans are coordinated by way of a timing means such that a succession ofpredetermined amounts of molten metal can be dispersed and delivered toa utilization device.

6. The apparatus of claim 1 wherein, both the impeller and poweringmeans are quick detachably coupled to the drive shaft.

References Cited by the Examiner UNITED STATES PATENTS 2/1959 GreatBritain.

I. SPENCER OVERHOLSER, Primary Examiner. R. S. ANNEAR, AssistantExaminer.

1. AN APPARATUS FOR THE DELIVERY OF MOLTEN METAL TO A UTILIZATION DEVICEWHICH COMPRISES A SUBMERSIBLE INTEGRATED PUMP-VALVE UNIT HAVING A PUMPASSEMBLY PORTION, SAID PUMP ASSEMBLY PORTIONINCLUDING A DRIVE SHAFTHAVING AN UPPER END AND A LOWER END, AN IMPELLER, SAID IMPELLER HAVINGTHE SAME LONGITUDINAL AZIS AS SAID DRIVE SHAFT AND BEING COUPLED TO SAIDDRIVE SHAFT, A PUMP CASING HAVING A TOP SECTION, BOTTOM SECTION, ANDSIDE WALLS, SAID CASING SURROUNDING SAID IMPELLER AND HAVING SUFFICIENTDEPTH TO PERMIT SUBSTANTIAL VERTICAL MOVEMENT OF THE IMPELLER INCONJUNCTION IWHT THE DRIVE SHAFT, SAID CASING HAVING AN INLET BORE MEANSIN SAID TOP SECTION, SAID DRIVE SHAFT EXTENDING THROUGH SAID INLET BORE,AND AN OUTLET BORE EXTENDING THROUGH SAID SIDE WALL, A VALVE ASSEMBLYPART, SAID VALVE ASSEMBLY PART INCLUDING A VALVE SEAT DISPOSED IN SAIDINLET BORE AND A VALVE HEAD, SAID VALVE HEAD SURROUNDING AND BEINGRIGIDLY COUPLED TO SAID DRIVE SHAFT; SUPPORTING MEANS TO SUSPEND THEAPARATUS IN THE MOLTEN METAL TO BE DIPENSED; POWERING MEANS TO PROVIDEROTARY POWER FOR THE PUMP PORTION; CTUATING MEANS FOR RAISING ANDLOWERING SAID DRIVE SHAFT WHEREBY SAID VALVE ASSEMBLY PORTION IS OPENEDAND CLOSED; AND A DELIVERY PIPE ATTACHED TO THE PUMP CASING AT SAIDOUTLET BORE.